Filter housing

ABSTRACT

Apparatus for filtering solid particles suspended in a gas includes a housing divided by a plate into an upper clean gas chamber and a lower polluted gas chamber. Depending filter elements are secured to apertures in the plate. Polluted gas flows to a distributor, in the lower chamber below the filter elements, to which is coupled a plurality of vertically disposed pipes extending upwardly past the filter elements to outlets disposed in the vicinity of the plate. The upward discharge from these outlets is then deflected downwardly past the filter elements.

The invention relates to a filter housing for separating a two-phasemixture consisting of gaseous and solid components, which is divided bya rigid plate provided with openings into a raw gas chamber located atthe bottom and a clean gas chamber located at the top above the raw gaschamber, whereby filter elements leading downwards into the raw gaschamber are secured in the openings of the rigid plate, a two-phase flowis introduceable into the raw gas chamber, the clean gas chamber has anoutlet located above the filter elements for the gaseous components ofthe flow freed from the solid components by the filter elements andcleaning devices are associated with the filter elements for flushingout the filter elements.

In filter housings of the specified type (DE-A1-40 29 395; FR-A1-22 44559), it is important for the two-phase flow to reach the individualfilter elements in a uniform manner, for turbulences of the flow to bereduced to a minimum and the flow velocity to have, as far as possible,more or less the same values throughout the filter housing.

This is particularly important for the cleaning of the filter elementsby means of a gas pressure pulse directed contrary to the two-phaseflow. Such cleaning normally takes place during the operation of thefilter housing, whereby the gas pressure pulse is merely applied to someof the filter elements while the remaining filter elements can continueto exercise their filtering function undisturbed. When the solids (dust)which are thereby separated from the filter elements and fall downwardsare picked up by the two-phase flow still prevailing in the housing anddirected essentially upwards, they will be whirled about, and anundesired resoiling of the filter elements can easily occur.

For this reason, attempts have already been made by using baffle plates,inclined introduction of the two-phase flow into the filter housing,flow distributors and the like to guide the two-phase flow entering theraw gas chamber such that it is, as far as possible, directed in thesame direction with the falling dust and prevents this from resoilingthe filter elements. Such a "uniform flow guidance" of raw gas andfalling dust can be adjusted in a relatively uncomplicated manner insmall filter housings having less filter elements. In the case of largefilter housings with numerous filter elements, high volume throughputsand/or high pressure losses and dust loads, the problem of resoiling hasnot so far been solved satisfactorily.

The object of the invention is to design a generic device such that thetwo-phase flow entering the raw gas chamber of the filter housing isdirected essentially downwards and guides dust falling from the filterelements towards the floor of the filter housing.

The object is accomplished in accordance with the invention, in ageneric filter housing, in that a pipe system extending at leastpartially in the interior of the raw gas chamber and branching betweenthe filter elements is provided for receiving the two-phase flow, thepipe system dividing the two-phase flow into at least two partialstreams and guiding these partial streams past the filter elementsupwards as far as the vicinity of the rigid plate where the partialstreams exit through openings out of the pipe system into the raw Gaschamber, and that deflecting means are arranged in the raw Gas chamberin the vicinity of the point of exit of the partial streams out of thepipe system, these deflecting means deflecting the partial streams inthe raw Gas chamber freely downwards.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of a preferred embodiment of the inventionserves to explain the invention further in conjunction with the attacheddrawings. In the drawings:

FIG. 1 shows schematically a filter housing with a pipe system servingto introduce a two-phase flow;

FIG. 2 shows schematically a plan view of a modified pipe system and

FIG. 3 shows schematically a rigid plate provided with openings forsupporting filter elements, whereby the filter elements are combined ingroups to form segments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The filter housing 1 of a conventional constructional type illustratedschematically in FIG. 1 comprises a funnel-shaped raw gas chamber 2located at the bottom and serving to separate dust and a clean gaschamber 3 located above it, these two chambers being separated from oneanother by a rigid plate 4. The plate 4 serves to support filterelements 5 which, in the illustrated case, are designed as downwardlyhanging filter cartridges made of a ceramic material. The filterelements 5 are arranged in openings in the rigid plate 4 so that a gasfrom the raw gas chamber 2 can flow through the filter elements 5 intothe clean gas chamber 3.

The raw gas chamber 2 has in a conventional manner an inlet 6 locatedbelow the filter elements 5 for a two-phase flow consisting of gaseousand solid components, for example a hot gas mixed with dust and sootparticles or the like. As illustrated, a pipe system 7 located in theinterior of the raw gas chamber 2 is connected to the inlet 6 and thispipe system comprises a central pipe 8, a distributor 9 connectedthereto and individual pipes 11 proceeding upwards from this. In theillustrated embodiment, a total of five, upwardly directed individualpipes 11 project symmetrically from the distributor 9, only four ofthese being indicated in FIG. 1. The fifth individual pipe is locatedbehind the central individual pipe 11. The individual pipes 11 are openat their ends located at the top in the vicinity of the underside of therigid plate 4. The two-phase flow entering through the inlet 6 branchesvia the central pipe 8 and the distributor 9 into partial streamsflowing through the individual pipes 11. These partial streams areconveyed by the individual pipes 11 past the filter elements 5 upwardsas far as the vicinity of the plate 4 where they exit out of the openends of the pipes 11 into the raw gas chamber 2. In this respect, thepartial streams are, as illustrated in FIG. 1 at the central individualpipe 11, deflected downwardly by the underside of the plate 4 acting asa baffle surface so that the direction of flow of the raw gas is nowturned parallel to the filter elements 5 downwards to the floor of theraw gas chamber 2.

Instead of deflecting the partial streams exiting from the individualpipes 11 directly by the plate 4, caps 12 covering the open ends of theindividual pipes 11 can also be used as deflecting means and these capsact as baffle plates. In any case, a raw gas flow--indicated in FIG. 1by the arrows 13--results and this is directed exclusively downwardsalong the elongated, cartridge-like or hose-like filter elements 5.

Due to the partial streams of raw gas which are first of all directedexclusively downwards in the interior of the raw gas chamber 2, it ispossible for dust falling from the filter elements 5 to be taken alongwith these partial streams downwards where it collects on the floor ofthe raw gas chamber 2. A "resoiling" of the filter elements 5 cannot,therefore, occur, such as happens normally when the raw gas flows fromthe inlet 6 directly upwards in the direction towards the plate 4 and tothe filter elements 5.

The raw gas which exits first of all at a relatively high velocity fromthe individual pipes 11 and flows downwards gradually decreases itsvelocity, reverses its direction and flows via the filter elements 5 andthe openings in the plate 4 associated with these upwards into the cleangas chamber 3, whereby solid components of the raw gas are retained bythe filter elements 5. The cleaned gas finally flows out of the cleangas chamber 3 through an outlet 14 arranged above the filter elements 5.

FIG. 3 shows schematically a bottom view of the plate 4. The individual,elongated filter elements 5 are combined into respective groups to formbundles or segments 15 which, for their part, are distributed over thesurface of the plate 4 leaving "alleys" or intermediate spaces free. Theindividual pipes 11 of the pipe system 7 which are directed verticallyupwards are arranged in these spaces. In this way, the incoming raw gascan be distributed uniformly to the individual filter elements 5 so thatthese can exercise their filtering function uniformly. (For the sake ofclarity, only one single segment 15 consisting of filter elements 5 isillustrated in FIG. 1).

FIG. 2 shows a pipe system which is modified in comparison with FIG. 1and in which, apart from a central individual pipe 21 which ispreferably provided, an additional six individual pipes 21 projectsymmetrically from a common central distributor 19. These individualpipes 21 which are directed vertically upwards parallel to the elongatedfilter elements 5 are also illustrated in FIG. 3 between a respectivethree segments 15 of filter elements 5.

As also indicated schematically in FIG. 1, a cleaning device 22 isassociated with a respective bundle or segment 15 of filter elements 5on the surface of the rigid plate 4 facing the clean gas chamber and therelevant filter elements 5 of this segments can be cleaned with thiscleaning device when required. The cleaning device 22 is advantageouslydesigned as counterflow ejector which allows the filter elements 5 to beacted upon in a manner known per se with gas pressure pulses directedinto the raw gas chamber 3, whereby solid particles which have collectedon the filter element 5 are separated so that they fall downwards. Thesedownwardly falling solid particles are not destroyed on their way to thefloor of the raw gas chamber by the inflowing raw gas since thislikewise has a strong, downwardly directed flow component in the mannerdescribed in the area of the filter elements 5. In this way, it ispossible to clean some of the segments 15 each time by the cleaningdevices 22 in the counterflow while the rest of the segments continue toexercise their filtering function. It has been found that with thisspecific cleaning procedure the downwardly directed partial streamsentering the raw gas chamber 2 from the individual pipes 11 favors thedeposition of the dust.

In the embodiments of the invention illustrated in FIGS. 1 and 2, thedistributor 9 or 21 is designed as a distributor chamber arrangedcentrally in the raw gas chamber. In modified embodiments, an annularline arranged peripherally in the raw gas chamber 2 or outside it couldbe provided instead of such a central distributor chamber, theindividual pipes 11 projecting from this line first of all essentiallyhorizontally and then vertically upwards towards the plate 4. In thecase of an annular line arranged outside the filter housing 1, branchlines project from this line radially and essentially horizontallythrough corresponding openings of the housing 1 into its interior.

The filter housing 1 described, with the pipe system 7 serving touniformly distribute the two-phase flow, is suitable for the cleaning ofoptional gas-solid mixtures. It is also particularly suitable for thecleaning of hot exhaust gases which can have temperatures of between100° and 1000°, preferably between 200° and 800° C. The system pressuresin the filter housing 1 are preferably between 0.75 and 50, inparticular 10 and 35 bar.

We claim:
 1. In a filter for separating a two-phase mixture comprisinggaseous and solid components, a housing divided by an apertured plateinto a lower polluted gas chamber and an upper clean gas chamber,wherein filter elements extending downwardly into the lower chamber aresecured in the plate apertures, the upper chamber having an outlet, thecombination including means comprising a piping system for introducingthe two-phase mixture into the lower chamber, the piping systemcomprising an inlet disposed below the filter elements and a pluralityof vertically extending pipes having outlets in the vicinity of theplate which discharge polluted gas upwardly, and means for deflectingthe upward discharge from each pipe downwardly past the filter elements.2. A filter as in claim 1 wherein the piping system comprises adistributor, the plurality of pipes being coupled to the distributor andhaving terminal portions extending in a substantially vertical directiontoward the plate.
 3. A filter as in claim 2 wherein the plate has anaxis of symmetry and wherein the distributor is axially disposed.
 4. Afilter as in claim 3 wherein the plurality of pipes have initialportions extending radially from the distributor.
 5. A filter as inclaim 1 wherein one of the pipe outlets is in proximity to the plate andthe deflecting means comprises the immediately adjacent area of theplate.
 6. A filter as in claim 1 wherein the deflecting means comprisesa cap disposed above a pipe outlet and having a downwardly extendingperiphery.
 7. A filter as in claim 1 wherein the filter elements aredisposed in groups having spaces therebetween and wherein the pipesextend upwardly in said spaces.
 8. A filter as in claim 7 furtherincluding means for cleaning the filter elements of a group.
 9. A filteras in claim 8 wherein the cleaning means includes a counterflow ejector.10. A filter as in claim 1 wherein the filter elements comprise hollowtubes.
 11. A filter as in claim 1 wherein the filter elements compriseceramic material.
 12. A filter as in claim 1 wherein the two-phasemixture has a temperature between approximately 200° C. andapproximately 800° C.
 13. A filter as in claim 1 wherein the pressurewithin the housing is between approximately 0.75 bar and approximately50 bar.
 14. A filter as in claim 1 wherein the pressure within thehousing is between approximately 10 bar and approximately 35 bar.